The best thing about a solo trip is that you can do exactly what you want to. If you want to go to MK every day, you can. You can go to the restaurant your travel companions hate. You can run from ride to ride all day or just sit and people watch. It’s all up to you. I would look up the most recent guide maps online, to get an idea of the changes since your last visit, so you can decide what are “must do” experiences for you.
I have done solo trips at both Pop and Port Orleans, and like them both. These days, I usually stay at Pop because I love the Skyliner. However, if you are considering traveling in the summer, be aware the Skyliner does not run when it storms (a daily occurrence in summer). They do run buses when it’s down, but it’s still a disappointment. As a solo, I also appreciate the room layout of the new Pop rooms, since I don’t have to lower the Murphy bed. It makes the room feel much more spacious. The resort has a kind of whimsical feel, from the bold colors and oversized decorations.
Port Orleans definitely has a more laid back feel to it, and if you plan to spend more time relaxing at your resort, it’s great. I prefer the French Quarter side, but have stayed at both. The rooms are a little larger, but as a solo you lose some of that space due to having two regular queen beds instead of being able to fold one up out of the way. The grounds are nice and PO feels a little more upscale than Pop. I don’t think you can really make a bad choice between those resorts.
WDW is one of the best places for a solo trip, in my opinion. CM’s are always willing to chat, if you start feeling too alone, and you can often strike up a conversation with other guests as well. I have never felt out of place, or like people even notice I am a solo. I eat in table service restaurants solo, ride attractions solo, book tours or special events solo, and never feel awkward. Actually, I have gotten to the point where I prefer my solo trips to the trips with family and friends.